Neurostimulation is the therapeutic alteration of activity in the central, peripheral or autonomic nervous systems by means of implanted devices. Neurostimulation may treat a variety of symptoms or conditions, for example, vagus nerve stimulation (VNS) is an adjunctive treatment for certain types of intractable epilepsy and treatment-resistant depression. A neurostimulator (or implantable pulse generator (IPG)) is a battery powered device designed to deliver electrical stimulation to the brain, central and peripheral nervous system.
The vascular system contains numerous locations within it and in contact with it which are electro-active and present the possibility of therapeutic electrical stimulation. One example of such a location is in the right brachiocephalic vein-SVC junction by which runs the right vagus nerve. Stimulation of the vagus nerve has been shown to result in an anti-inflammatory effect and a reduction in sympathetic drive which is beneficial to patients suffering from a variety of conditions including, for example, heart failure, acute ischemic attack, and atrial and ventricular arrhythmias.
Other locations are in the arterial system. One example of such a location is the carotid artery, especially the region in or around the carotid sinus, common carotid artery, the internal carotid artery and/or the external carotid artery. Also possible are other locations like the renal artery for stimulation of renal nerves, for example.
Trans-vascular stimulating electrodes exist for chronic application, for example, for phrenic nerve stimulation; however, most of them are designed for small vessels and cannot be used in large veins. Hence, a system capable of delivering or recording electric fields in a vessel near a neuroactive target location being compatible with large veins would be advantageous.
Trans-vascular stimulation of the vagus nerve has been demonstrated previously with basket catheters. One problem with common expandable basket-style stimulation catheters is that they are designed for acute stimulation and are not appropriate for chronic stimulation.
In common intravascular neurostimulation devices, electrodes are positioned within a blood vessel (for example, a jugular vein, superior vena cava, or inferior vena cava) and are used to trans-vascularly stimulate nervous system targets located outside or within the walls of the vasculature. For maintaining the electrodes in contact with the blood vessel wall anchors have been developed. Such anchors include structural features that allow the anchor to radially engage a vessel wall. The anchor may include a band, sleeve, mesh or other framework formed of shape memory materials (for example, Nitinol or shape memory polymer) or other non-biodegradable materials like, for example, stainless steel. However, safe explant of the electrodes at a later date, even after many years of biological interaction, may be desired, which cannot be achieved in presence of permanent anchors since they will be encapsulated fast by the biological system. In addition, continuous mechanical interface against the vessel wall with pressure from the anchor or stiff materials used in an anchor is not desirable because of its potential to cause vessel irritation and enlarged capsule formation.
Trans-vascular stimulation is also performed in cardiology, where the same drawbacks apply. For multi-chamber pacing of the heart it is commonly known to implant cardiac stimulation electrode leads within the coronary vein system, in particular within the Coronary Sinus vein (“CS”), in order to stimulate cardiac tissue, especially the left atrium and/or chamber. For anchoring of these electrode leads several anchoring mechanisms are known, which are mostly not explantable. For example, special formed parts of the lead such as helically shaped bodies are known to those familiar with the art. In this embodiment, stimulation pulses are provided by cardiac pacemakers, cardioverter or implantable defibrillators, which are also summarized with the term “implantable pulse generator”.
The present invention is directed toward overcoming one or more of the above-mentioned problems.